Chevrolet 1998 Astro Owner's Manual page 91

The power door lock switch will lock or unlock the rear
hatch and Dutch doors. See "Hatch Release" in
this section.
Every vehicle with power door locks has a pulse lock
system. A pulse lock system works like this:
If the sliding door is open and you press the power door
lock switch, the sliding door will not lock immediately.
After you close the door, the system comes on and, in
about five seconds, locks the sliding door.
All models have overriding door locks. When a door
is locked, the inside door handle will not work the
latch. This will help stop a door from being
accidentally opened.
Leaving Your Vehicle
If you are leaving the vehicle, take your keys, open your
door and set the locks from inside. Then get out and
close the door.
Keyless Entry System (Option)
If your vehicle has this option, you can lock and
unlock your doors or unlock your rear hatch from about
3 feet (1 m) up to 30 feet (9 m) away using the remote
keyless entry transmitter supplied with your vehicle.
Your keyless entry system operates on a radio frequency
subject to Federal Communications Commission (FCC)
Rules and with Industry Canada.
This device complies with Part 15 of the FCC Rules.
Operation is subject to the following two conditions:
(1) this device may not cause harmful interference,
and (2) this device must accept any interference
received, including interference that may cause
undesired operation.
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